Processing systems which expose workpieces such as, semiconductor wafers or other suitable substrates, to an overall treatment regimen for forming a particular device generally employ a plurality of treatment steps. In order to sequentially carry out these steps, each workpiece is typically moved a number of different times, for example, into the system, between various processing stations and out of the system. With the foregoing in mind, it is noted that the prior art contains a number of alternative approaches for use in performing such workpiece transfers and related functions, certain ones of which are interest here, as will be described in further detail immediately hereinafter.
One prior art workpiece transfer approach is demonstrated in U.S. Pat. No. 6,429,139 (hereinafter the '139 patent). More specifically, the '139 patent, in FIGS. 5, 6 and 7A-D, illustrates the use of an articulated robot arm for use in workpiece transfer. While the use of a single wafer paddle is illustrated, it should be appreciated that multiple paddles have been provided using such an articulated robot arm. It should also be appreciated that this particular robot is somewhat simplified to the extent that the prior art provides such a configuration in which vertical movement of the workpiece is also accomplished by the robot. While such articulated robotic arm configurations effectively provide essentially unlimited capabilities with respect to moving workpieces, unfortunately, they are relatively complex and, therefore, expensive to manufacture and maintain.
A simple swing arm, as taught by the prior art, generally comprises an arm member which extends from a pivot point to a wafer paddle. Such a swing arm, therefore, provides for rotational motion of a workpiece. While a swing arm configuration represents a dramatic simplification over the use of an articulated robotic arm, at least generally thought to be accompanied by improved reliability and lower cost, it also represents far more limited capabilities with respect to wafer positioning. Specifically, the swing arm, in its basic configuration, is capable only of moving one wafer along a single diameter, planar circular path. One early swing arm approach is seen in U.S. Pat. No. 4,927,484 (hereinafter the '484 patent). FIGS. 1 and 2 of this patent demonstrate a typical prior art approach in which a plurality of simple swing arms cooperate in order to provide greater workpiece movement flexibility. Again, however, these swing arms appear to be limited to rotation of a workpiece in a single plane.
As an alternative approach to the articulated robotic arm and an improvement over the simple swing arm, the '139 patent also teaches the use of a double-ended swing arm arrangement. Swing arm capability is enhanced through providing an elongated swing arm member having a wafer paddle positioned at each of its opposing ends, with a pivot point centered therebetween, as can be seen in FIG. 8A of the '139 patent. Further, the '139 patent, as seen in FIGS. 9A-D, describes wafer paddles that are rotatable at the ends of the swing arm member so as to at least somewhat improve the positioning capabilities and flexibility of the swing arm over earlier prior art configurations. Unfortunately, however, swing arm positioning capabilities remain limited, despite these improvements, particularly with respect to the capability to move the wafer only in one plane of rotation.
A more recent approach with respect to the use of a swing arm is seen in U.S. Pat. No. 6,610,150 issued to Savage et al (hereinafter Savage). Savage illustrates, in FIG. 8 of the patent, a swing arm having an end effector that is configured for supporting a pair of workpieces. Like the remaining prior art, only simple rotational motion is described wherein typical prior art expedients such as lift pins are used to remove a workpiece from the end effector.
Another area of concern with respect to prior art workpiece processing systems resides in the door arrangements that are used to seal various portions of the system from one another. Many systems utilize, for example, a loadlock chamber (i.e., a chamber that facilitates both workpiece load and unload functions), a transfer chamber and one or more process chambers. Workpieces are typically transferred between the loadlock chamber and the process chamber through the transfer chamber. It is necessary, in such a configuration, to selectively seal the loadlock chamber from the transfer chamber. For purposes of workpiece transfer, a slot or slit is generally defined between the two chambers. Sealing is often performed using a slit door arrangement in which a platelike door member is used to seal the elongated slit. Concerns with respect to prior art slit door arrangements include contamination production, the need for precision alignment and sealing mechanisms.
One prior art slit door configuration is described in U.S. Pat. No. 6,095,741 (hereinafter the '241 patent) having a blade member which is hinged to its actuation arm for pivotal movement about a horizontal axis. This arrangement is considered to be unacceptable, particularly with respect to precision alignment of the elongated, horizontal dimension of the sealing blade and the potential production of contaminants in the absence of such precision alignment, as will be appreciated in view of the descriptions which follow.
With respect to sealing mechanisms, the '241 patent uses a bellows as part of its slit door arrangement, illustrated as item number 704 in FIG. 6A of the patent. While such a bellows mechanism may be effective for purposes of the '241 patent, it is considered as problematic for reasons which include cost and reliability concerns. As will be further described, the prior art has adopted other approaches as alternatives to the bellows mechanism.
One such alternative to the bellows mechanism is illustrated in FIG. 29, which is a partially cutaway view of a prior art slit door configuration that is generally indicated by the reference number 1700. This prior art configuration includes a pivot shaft 1702 that is connected at an upper end to a sealing blade (not shown) for pivotal motion, as indicated by a double headed arrow 1704 about a pivot axis 1706. Pivot shaft 1702 is received in a housing 1710. Sealing between housing 1710 and pivot shaft 1702 is accomplished using a seal flange 1712 that is received on housing 1710 and sealed thereagainst using an O-ring 1714. A seal hat 1716 is supported on pivot shaft 1702 and sealed thereagainst using an O-ring 1718. Seal hat 1716 supports an O-ring 1720 for sealing against a sealing surface 1722 that is defined by seal flange 1712 such that side-to-side motion of O-ring 1720 against sealing surface 1722 is accommodated. Unfortunately, however, pivotal motion of pivot shaft 1702 also imparts tilting of seal hat 1716 thereby compressing one portion of the O-ring 1720 while releasing an opposing portion of the O-ring. This behavior is disadvantageously considered to limit the range of pivotal motion of pivot shaft 1702.
The present invention resolves the foregoing limitations and concerns while providing still further advantages.